The Public Switched Telephone Network (PSTN) can be inefficient. There are a number of invalid network conditions that consume network resources without providing benefits to the network and indeed may, at times, produce service impairment in the form of blocked calls. In addition, there are a number of valid, yet undesirable, telecommunications events that waste network resources. Examples of these invalid conditions and undesirable events include, for example, call looping, misrouted traffic, unreported mass calling, and excessive redialing.
A call looping condition occurs when a telephone call originated by a calling party to a called party loops on a trunk group between an originating end office (“EO”) and a terminating EO multiple times. Such looping condition can occur due to a number of situations including, for example, errors in translation tables that are provisioned at one or both of the EOs. When it occurs, the looping condition uses up multiple members, and perhaps all members, in a trunk group, blocking legitimate calls, resulting in inefficiency and service impairment in the network. When all members in the trunk group between EOs are used as a result, the looping condition results in a reorder, meaning the calling party would hear a 120IPM (or fast busy) signal, and would have to redial the called number. Some of these looping conditions are never noticed by the calling party, however, because a call could ultimately be routed to the desired called party after several looping iterations. Accordingly, many of these conditions have gone undetected and the network has unknowingly wasted its resources. This results in building a larger network, sometimes substantially so, than would otherwise be required by a network provider.
A misrouted traffic condition occurs when a call originated by a calling party to a called party is misrouted to one or more tandem offices that would not normally be involved in completing the call. For example, in a metropolitan area that has five tandem offices, namely, Tandem Offices A through E, a call originated from an originating EO associated with Tandem Office A to a terminating end office associated with Tandem Office E would normally involve resources of one trunk group linking Tandem Office A to Tandem Office E. The misrouted traffic condition occurs when Tandem Office A, instead of routing the call to Tandem office E, misroutes the call to one or more of Tandem Offices B, C, and D. For example, the call may be misrouted such that it “snakes” from Tandem Office A to Tandem Office B, from Tandem Office B to Tandem Office C, from Tandem Office C to Tandem Office D, and finally from Tandem Office D to Tandem Office E, using up resources of four trunk groups. This misrouted traffic condition is also referred to as a “snaking condition” (by the inventors, at least).
A mass calling event occurs when multiple calling parties call a common called party simultaneously, or within a short period of time. One example of such mass calling event is associated with radio station call-ins. For example, when a radio station conducts a survey or a contest during which the general public is invited to call the radio station immediately or within a specific time frame, thousands of telephone calls would be originated by listeners. As known in the art, such mass calling of a common called party results in significant stress to the network, particularly if the radio station does not warn the network provider ahead of time. Such a mass calling event can, among other things, aggravate the call looping and misrouted traffic conditions described above.
An excessive redialing event occurs when a calling party, within a relatively short time frame, repeatedly dials one or more called numbers. For example, excessive redialing can occur when a calling party repeatedly dials the same called number until connected. Redialing can be accomplished either manually or by invoking a feature of the telephone set used by the calling party. Excessive redialing can also occur when the calling party sequentially dials a number of called numbers. This can happen, for example, during a telemarketing campaign in which a computer is used to dial large number of potential customers' telephone numbers. As known in the art, such excessive redialing results in significant stress to the network. Such excessive redialing also aggravates the call looping and misrouted traffic conditions described above. This is most apparent when a Customer Premise Equipment (CPE) device, such as a PBX, uses an ISDN protocol to “flood” network with call setup messages.
Accordingly, these invalid and undesirable conditions use up valuable network resources, and they are costly to telephone networks.
Prior to the present invention, there was no known solution to the problems summarized above. The closest known technology is a switch-based “hop counter” that ensures that a message is not excessively looped under certain conditions. The basic operation of the hop counter can be briefly described as follows. A telephone network provisions a hop counter on a trunk group at a switch, and sets a default number to ten. Each time a call is routed to a network element, which is capable of understanding the hop counter capability, or back to the originating switch, the hop counter is decremented by one. When the call routes for the tenth time, the call is dropped, thereby preventing excessive looping condition. As known in the art, the hop counter does not help detect the root cause of the looping condition, nor does it detect all looping conditions. For example, the hop counter technology that exists today is not capable of finding errors in translation tables, which may cause the looping condition.